Focal Utopia Be 21 WX (SVC 4 ohm)

8″ subwoofer · 4 Ω · 250 W RMS

Fs 36.6 HzQts 0.60Vas 0.66 ft³Xmax 0.33″

Recommended box

For a sedan, one sub, 250 W. It’s the same math as the designer’s step-by-step mode, where you can fit the box to your space, vehicle and amp and get plans, a cut sheet and DXF.

Sealed

Net volume0.74 ft³ (21 L)
Qtc0.83
Fc50 Hz
F3 (−3 dB, no cabin gain)46 Hz
Example box (outside)11″ × 11″ × 15 15/16″
Open sealed box in designer

Ported

Net volume1.24 ft³ (35 L)
Tuning (Fb)34 Hz
Portslot 1 9/16 × 14 5/16″, 38 5/16″ long
Port velocity at 250 W39 ft/s
F3 (−3 dB, no cabin gain)30 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 9 1/4″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs36.6 Hz
Qts0.60
Qes0.77
Qms2.81
Vas0.66 ft³
Re3.4 Ω
Sd32.3 in²
Xmax0.33″
Vd10.8 in³ calc.
Mms62 g calc.
BL7.9 T·m calc.
EBP48 — suits sealed calc.
Sensitivity, 1 W / 1 m82.8 dB calc.

General

Size8″
Voice coils4 Ω
RMS power250 W

Mounting dimensions

Ø8 9/16″cutout ≈ Ø7 11/16″mounting depth 4 3/16″magnet Ø≈ 5″
Cutout diameter≈ 7 11/16″
Mounting depth4 3/16″
Overall diameter8 9/16″

“≈” means the value isn’t in the spec sheet and a typical value for the size is used; “calc.” means it’s calculated from the published parameters. Check the manufacturer’s spec sheet before you build.

Data sources

Other Focal 8″ models